Method of treating zinc ores



Oct. 18, 1932. 1.. w. LENNOX ET AL 1,383,234

METHOD OF TREATING ZINC QRES Original Filed Feb. 7, 1929 zmc ORE OR CONCENTRATE CONTA\N\NG A Pb, cu, Au, 5

PREUMWARY ROAST \N STRNGHT UNE ROASHNG FURNACE TO REDUCE DRNEN OFF SULPHUR CONTENT TO ABOUT \76 TO 2% Nam Add 5. Pb Au, A9 1 Cu v BAG HOUSE OR WASH TOWER CHLOR\D\Z\NG ROAST WH'H 0U OFF m STR mam uue RoAsTme FURNACE USUAL ZmC 1H Ag u SMEL'HNG mama Y BAG HOUSE OR WASH TOWER avw toz 411a fig q Mfluomm 2 W M. M

LUTHER WILLIS LENNOX, OF PALO ALTO, CALIFORNIA, AND HORATIO SEYMOUR WILDHAN, F VILLA ESCOBEDO, CHIHUAHUA, MEXICO, ASSIGNOBB T0 AMERICAN BHELTING & BEINING COMPANY, OF NEW YORK, N. Y A CORPORATION OF NEW JERSEY METHOD OF TREATING ZINC OBES Application filed February 7, 1929, Serial No. 888,082. Renewed April 25, 1982.

The invention relates to the metallur of zinc, and more particularly to a methgd of chloridizin certain metals which may be contained in zinciferous material before .5 treating such material to recover the zinc.

According to the invention certain impurities, such as lead and copper, frequently associated with zinc in zinc ores, and also precious metals, are effectively removed by sub'ecting the zinc bearing material to a ch orides.

It has been found that sodium chloride is a suitable reagent for use in the chloridizing roast to increase the percentage of impurities volatilized. It has also been found that this reagentis beneficial in the subsequent treatment of the zinc bearing material in the usual zinc smelting furnaces for recovering the zinc.

Various other features and advantages of this invention will be apparent from the following particular description of the several steps employed in practicing the same and from an inspection of the accompanyingv drawing comprising a flow sheet illustrating the process, and it will be understood that the said steps ma be modified in various respects without e arting from the broad spirit and scope .0 the invention.

The complex zinc ores or zinc concentrates containing various metals as impurities, such as lead, cop r, silver and gold, are charged into a suita 1e roasting furnace, prefers ly of the strai ht line type, such as an Edwards, Ropp or 'nner furnace and the sulphur content'is reduced to approximately one percent'if practical. However, reductlomto two percent or less of sulphur is sufli'cient in most cases, and with some ores a reduction to three rcent or less givessatisfactory ome of the meta impurities,

cially lead, may be driven 03 in this preliminary or oxidizing roast, so it is desirable that provision be made to collect the fume in a suitable manner as ima'bag house or wash tower.

After the preliminary or" oxidizin roast, and preferably while the charge is sti l in the roasting furnace and without necessarily lowering the temperature to any substantial extent, a chloridizing agent such as sodium chloride is mixed therewith. The mixture is then subjected to a second roasting operation. The quantity of the chloridlzing agent is determined, of course, by the percentage and the character of the impurities in the char e. The temperature is so regulated that t e greater part if not all of the metals other than zinc are driven off as chlorides without volatilizin the zinc. These metals comprise practica dy all of the remaining lead, copper, gold an silver. In addition a substantial amount of the remaining sulphur is also driven oii. Suitable means for the recovery of the fume, such for example as wash towers or bag houses are provided or a Cottrell high voltage precipitation apparatus may be used.

The resulting product from the second roasting operation is removed from the roaster and is subjected to any desired or usual zinc smelting treatment to recover the zinc.

Any small amount of uncombined salt orother chloride remaining in the roastis not deleterious but is frequently advantageous in the subsequent step of retort smelting. It

will be obvious that the chloridizing-roast may be carried out in another furnace or in a separate apparatus alt-hon h the additionof the p'roper reagent to the c arge without removing it from the furnace conserves heat and saves time.

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The process of treating zinc-bearing materials of a sulphide character containing metallic impurities including lead, which comprises subjecting the zinc-bearing material to an oxidizing roasting treatment to remove sulphur fromsaid material, discontinuing said roasting treatment when the content of'sulphur has been reduced to less than about 3%, mixing sodium chloride with said roasted ore having a sulphur content of less than about 3% without lowering the temperature of said roasted ore to any substantial extent, subjecting the mixture of roasted ore and sodium chloride to heat sufliciently intense to fume ofl metallic impurities including lead but insuflicient in intensity to cause the volatilization and loss of zinc, and thereafter smelting said zinc-bearing materials freed from lead to eflect a recovery of zinc therefrom.

2. The method of treating complex zinc ores and concentrates of a sul hide character containing impurities inclu ing substantial amounts of lead, copper, gold and silver, which comprises subjecting said ores and concentrates of zinc to an oxidizing roasting treatment ina straight line roasting furnace, continuing said roasting treatment until the sulphur content is reduced to an amount less than about 3%, after the sul hur content has been reduced as aforesaid an before the said roasted ore has been' lowered in temperature to any substantial extent mixing sodium chloride with the roasted zinc material containing less than about 3% of sul hur, heating the mixture of sodium chlori e and zinc material in a straight line roasting furnace to a temperature sufliciently high to fume ofi metallic impurities including lead, gold, silver and copper, but not high enough to volatilize zinc, continuing said heat treatment to effect a removal of metallic impurities includin lead, gold, silver and copper and therea ter smeltin the zinc material freed from lead, gold, s' ver and copper for the recover of Z1110.

3. he method of treating zinciferous material of a sul hide character containing impurities inclu ing lead, gold, silver and copper, which comprises sub ectin' the said zinciferous material to an oxidizing roasting treatment in a straight line roasting furnace,

discontinuin said oxidizing roasting treat- I ment when t e sulphur content of the mate'- rial has been reduced to an amount less than about 3%, while said-roasted material is in a heated condition mixing a chlorine containing agent with said roasted material having a sulphur content thereof reduced to less than about 3%, heating the mixture of roasted zinciferous material having a sulphur content less than about 3% and said chlorine containing agent to a temperature suificiently high to fume ofi metallic impurities including lead, gold, silver and copper, but insufficient to cause the volatilization and loss of zinc and then smeltin said purified zinciferous material freed rom lead, gold, silver and copper for the recovery of Zinc.

In testimony whereof we have hereunto set our hands.

LUTHER WILLIS LENNOX.

HORATIO SEYMOUR WILDMAN. 

